Basic Science-Anatomy

The thoracic outlet may be considered as a space between the relatively fixed, immobile thorax, particularly the first rib and clavicle, extending to the anterior and middle scalene muscles and under the pectoral tendon and coracoid process laterally.

The brachial plexus forms from the fifth cervical to the first thoracic nerves after they exit from their respective intervertebral foramen. The anterior and middle scalene muscles take their origin from the transverse processes of the upper cervical spine and insert on the first rib.

The brachial plexus and the subclavian artery, which leaves the chest off the aortic arch, travel between these two muscles, over the first rib, and beneath the clavicle. The subclavian vein travels over the first rib anterior to the anterior scalene before joining the subclavian artery and brachial plexus.